In several countries the army is officially
called the land army to differentiate it from an air force
called the air army, notably France. In such
countries, the word "army" on its own retains its connotation of a
land force in common usage. The current largest army in the world
by number of active troops is the People's
Liberation Army of China with 2,250,000
active troops and 800,000 reserve
personnel.

Field army

A field army is composed of a headquarters, army
troops, a variable number
of corps, and a variable
number of divisions.
A battle is influenced at the Field Army level by transferring
divisions and reinforcements from one corps to another to increase
the pressure on the enemy at a critical point. Armies are
controlled by a General or Lieutenant General.

Formations

A particular army can be named or numbered to
distinguish it from military land forces in general. For example,
the First
United States Army and the
Army of Northern Virginia. In the British Army
it is normal to spell out the ordinal number of an army (e.g. First
Army), whereas lower formations use figures (e.g. 1st
Division).

Armies (as well as army groups
and theaters)
are large formations which vary significantly between armed forces
in size, composition, and scope of responsibility.